Circuit for energizing at least one gaseous electric discharge device



Aug. 5, 1958 D. KAYSER 2,346,619

CIRCUIT FOR ENERGIZING AT LEAST ONE GASEOUS ELECTRIC DISCHARGE DEVICE Filed Nov. 21, 1955 All Patented Aug. 5, 1958 has ClRCUlT FQR AT LEAST (ENE GASESUS ELECTRIQ DISQHARGE DEVICE Daniel Kayser, Farris, France, assignor to Societe Anonyrne pour les Appiications de lElectrir-ite ct ties Gan Rares-Etablissements Claude-Fez & Silva, laris, France Application November 21, 1955, Serial No. 54%,204

Claims priority, appiication France November 26, 1954 6 (Ilaims. (Cl. 315-2S2) This invention relates to a circuit for energizing at least one gaseous electric discharge device and including a transformer having a large magnetic leakage, which transformer comprises a primary winding connected with the current source through a condenser and at least one secondary winding energizing a discharge device or sev eral discharge devices connected in series.

It is known to energize a fluorescent lamp, for eXampie, by means of such a circuit. When, however, the discharge device is disconnected, or cannot start or even merely operates with rectified current because one or" its electrodes is worn out, it will be found that a high current is caused to how through the primary winding of the transformer and through the condenser in series, which high current may result in damage to those elements.

The circuit according to the invention does not offer these drawbacks. It is characterized by the fact that at least the greater part of the secondary winding of the transformer is shunted, possibly through at least a portion of the primary winding, by a resistance which is semiconducting and the value of which remains high when the nominal discharge occurs in the discharge device, such value decreasing largely and gradually when the discharge current in the discharge device is nil or very small during at least every other half-cycle.

It would seem, a priori, that in order to prevent the flow of a high current, in the portion of the circuit consisting of the primary and the condenser, due to the circuit being close to resonance, the semi-conducting resistance should shunt either said primary winding or the condenser. It has been found on the contrary, that much better results are obtained by shunting an element outside the aforesaid circuit portion, namely the econdary winding of the transformer. It is possible to shunt also, by means of the resistance, part of said circuit portion, for example part or all of the primary Winding, but good results can be obtained only by including in whatever is shunted, the secondary winding or at least the greater portion thereof.

This improvement of the results arises from the fact that, when the semi-conducting resistance is arranged according to the invention the value of the ratio of the voltages to which it is subjected is relatively far from unity, the ratio being of the voltage in normal operation to that when the discharge device is disconnected or much worn.

This ratio would be closer to unity if the resistance were placed across the terminals of the primary winding alone or of the condenser. In such a case, the choice of the resistance for a given energizing circuit is difiicult because it can be made only between close limits of the characteristics. in addition, the resistance may operate, i. e. heat up to such a point that its value becomes very small, untimely, or, on the contrary it may not operate when it should, for example in certain conditions of ambient temperature.

The invention will be better understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

Figure 1 shows a circuit for energizing two discharge devices.

Figure 2 shows a circuit comprising a transformer with separate windings for the energizing of one discharge device.

Figures 3 and 4 represent circuits with an autotransformer for the energizing of a discharge device, the voltage across the terminals thereof being higher, for an equal voltage of the current source, in the case of Figure 3 than in the case of Figure 4.

Figure 1 shows, diagrammatically, a two-lamp, high power factor, circuit, for the starting and stabilizing of two discharge lamps 7 and 12 energized by an alternating current source 9, it

The lamp 12, with an inductive stabilization, is energized by the secondary winding 1 of a transformer having magnetic leakage, the primary winding 11 of said transformer being connected to the current source 9, 1 A magnetic shunt 2, placed between the primary and secondary windings, sets up, in this transformer, magnetic leakages which cause a large leakage reactance therein. This reactance decreases the voltage delivered by the transformer, the more so as the current it delivers is larger and it results in the stabilisation of the discharge in the iamp 12 and in the production, by the transformer, of a voltage, under load, much smaller than its open circuit voltage.

The lamp 7, with a capacitive stabilisation, is energized through the secondary winding 5 of a transformer the primary winding 3 of which is connected with the current source 9, ll through a condenser 3. This transformer, which may be of the same design as the trans former ll, 1, offers large magnetic leakages, due, to example, to the presence of a magnetic shunt 4.

The condenser 3 otters, at the frequency of-the current source, 9, 16, a capacitive reactance of the order of twice the inductive reactance, with a normal load, of the transformer 8, 5 as measured at the primary winding thereof. The combination of tiis capacitive reactance and of this latter inductive reactance stabilizes the discharge in the lamp 7 and lowers very largely the voltage under load of the secondary winding 5 with respect to its open circuit voltage.

As compared with a one lamp circuit, the circuit illustrated in Figure 1 results in a very large decrease of the flickering, or stroboscopic effect of the light radiated by the assembly of the lamps 7 and 1.2, when these are used for the light they give out. in addition, the power factor of the current, taken at the source 9, it), is close to unity, at the same time as the circuit impedance remains high as concerns currents with frequencies definitely higher than that of the current source. These two latter features are advantageous even when the lamps 7 and 12 are not utilized for supplying light, for example when they are germicidal lamps.

ne circuit as described above, is known. It ofifers, with respect to the circuits in which the phase shifting condenser is in series between the lamp With a capacitive stabilisation and the secondary winding 5 for this lamp, the advantage that the secondary winding only has to supply a much lower voltage, namely the same voltage as the secondary winding 1 energizing the lamp 12 of the same type, but stabilized inductively. It offers, on the other hand, a fairly serious drawback. When the winding 5 does not deliver any current, for example when the lamp 7, worn out or damaged, cannot start, the transformer 8, S is open circuited and its inductive reactance, on the primary side, increases and compensates approximately the capacitive reactance of the condenser 3. A very large current than flows in the circuit 16,

3, 8, 9 of the primary winding of the transformer. This current may burn the primary winding 8 of the transformer and causes between the armatures of the condenser 3, a voltage which will stress the latter and may cause its breakdown.

According to the present invention, this drawback is obviated by shunting the secondary winding 5 by a suitable thermistance 6. A thermistance is a resistance, of the semi-conducting type, the value of which is very substantially higher when it is cold than when it is hot. In the present case, when the thermistance 6 is subjected only to the normal operating voltage of the lamp 7, it does not heat up much if it has been suitably chosen, and passes only a small current with said voltage. On the contrary, when the thermistance is subjected to the open-circuit voltageof the secondary winding 5, which voltage is two to four times larger than the op erating voltage for the lamp, a current flows through it, which, when it is cold, is several times larger than in the previous case. This current heats the thermistance much more and, hence produces a still more pronounced decrease of its resistance, which causes an additional heating, and so on. If the thermistance 6 has been suitably chosen, it passes, after being energized for some time under the voltage of the secondary winding 5 when no current flows through lamp 7, a relatively important current of the same order of magnitude as the normal discharge current in the lamp 7. The inductive reactance of the transformer, measured on the side of its primary winding 8 then decreases largely and the current returns to normal in the circuit 10, 3, 8, 9.

A similar process occurs when lamp 7 rectifies strongly, that is when the discharge current is very distinctly lesser than the normal dischargecurrent, or even is nil, every other half-cycle: during these half-cycles the voltage at the terminals of the lamp is near the no-load voltage of the secondary winding if thermistance 6 has not yet become hot.

The thermistance 6 should have a cold resistance and an inertia sufficient for not decreasing excessively the voltage supplied by the secondary winding 5 during the few seconds that may be required by a diflicult starting of the lamp 7. For instance, in the case of a watt fluorescent lamp 1.20 m. long and with an inner diameter of 38 mm., started with no pre-heating of its electrodes but provided with an outer starting band connected with one of its electrodes through a resistance of about 100,000 ohms, the open circuit voltage of the secondary winding 5 is about 320 volts, its voltage under load about 105 volts. Under that load voltage, when the ambient temperature is 40% C., the thermistance 6 will reach a temperature of approximately C. and

will pass about 2 to 3 milliamperes. When the lamp 7 is started normally or almost normally, the thermistance will not have been subjected to a high voltage for a sufficient time for its resistance to have dropped substantially.

When the secondary winding 5 delivers current to the thermistance only, the latter, after 3 to 5 minutes, reaches a temperature of about 350 (1., at which its resistance has dropped very largely. The thermistance 6 then passes a current of about 0.5 amp. The voltage at the terminals of the secondary winding 5 which then passes a current slightly higher than its normal load, is, at, that time,-very close to 25 volts. After some time, the temperature of the thermistance stabilizes around 350 to 400 C. It then draws a current of about 0.5 amp. and the current through the condenser 3 and the primary winding 8 is 0.75 amp. If the transformer 8, 5 were made to operate in open circuit, the thermistance '6 not being utilized, a current of 1.2 amp. would flow through the primary winding of said transformer and the voltage across the terminals of the condenser 3 would be 300 volts, instead of 1 amp. and 220 volts respectively in normal operation.

Figure 2 shows, diagrammatically, a circuit for the energizing of a single lamp with a capacitive stabilisation. This circuit is very similar to the portion of the circuit represented in Figure 1 relative to the energization of the lamp 7.

It offers, however, a difference. In Figure 2 14 denotes an inductive reactance, such reactance shunting the current source 9, 10. This reactance is used when the current drawn is desired to have a good power factor, while using, for the transformer 5, 8 and for the con: denser 3 the same apparatus as for the energizing of the lamp with the capacitive stabilisation of a two-lamps group similar to that shown in Figure 1. The reactance 14 is omitted when the lamp energized by the circuit of Figure 2 is utilized at the same time as one or more lamps with an inductive stablisation, so as to correct, to a certain extent, the power factor and the flickering of the latter lamp or lamps.

For lamps 7, 12 of a given type, the transformers 8, 5 and 11, 1 may be of the same model as may the condensers 3, While allowing the possibility of diiferent circuits for instance a high power factor, two-lamps, assembly (circuit in Figure l), a single lamp circuit with a power factor close to unity (lamp circuit of Figure 2 with the reactance M), a single lamp circuit with an inductive stabilization (left hand half of the circuit of Figure l), a single lamp circuit with a capacitive stabilisation (circuit of Figure 2 without the reactance 14).

Figure 3 shows, diagrammatically, a circuit which differs from that of Figure 2 only in that the transformer 5, S is an autotransforrner and not a transformer with separate windings. This makes it possible to decrease the number of turns in the windings 5 and the section of the wire in the primary winding 8. The windings 8 and 5 are connected by a connection 15 and it is the voltage across the terminals of the assembly of the wind ings 5 and 3 which is applied to the lamp 7 and to the thermistance 6. If desired the thermistance may be arranged to shunt only the winding 5.

Figure 4 represents a modification of the circuit of Figure 3 and it can be used when the transformer 5, 8 is an auto-transformer and when, the starting voltage of the lamp 7 not being sutliciently higher than the source voltage, the secondary winding 5 would have too few turns for the operation of the lamp 7 to be stable. In

this circuit, the secondary winding is connected by a' connection 27, not to one end of the primary winding but to an intermediate tap 16 thereof. The winding 5 can thus be given a sufficient number of turns while decreasing the size of the windings as compared with those which would be required by a transformer with separate windings.

The left hand end of the thermistance 6, the one which is not connected with the end of the secondary winding 5 not connected with the primary, may be connected either with the end of the primary winding connected with the lamp as in Figure 4 or with the tap 16.

In this case, again, a reactance coil 14 may be used for improving the power factor.

Numerous modifications may be made to the above described circuits within the scope of the present invention. For instance, each transformer may be of the shell type, in which case it is necessary to have not one, but two magnetic shunts such as indicated at 4. The magnetic shunts may be omitted when the coils 5 and ii are sufficiently spaced so that the magnetic leakages in air give the transformers a sufiicient reactance. Each one of the lamps may be replaced by several lamps mounted in series and starting either simultaneously or successively.

What I claim is:

V 1. A circuit for energizing at least one gaseous electric discharge device, comprising: an alternating current source; a high reactance transformer having a primary winding and at least one secondary winding; means for connecting said primary winding to said source through a condenser; means for connecting said secondary winding to said discharge device; and a semi-conducting resistor the resistance of which remains high when it is subjected to the voltage of said secondary winding under load and decreases largely and gradually when said resistor is subjected to the open circuit voltage of said secondary winding during at least every other half-cycle, said resistor being connected in parallel with said secondary winding.

2. A circuit as defined in claim 1, comprising an inductive reactance connected in parallel with the source of current.

3. A circuit for energizing at least one gaseous electric discharge device, comprising: an alternating current source; a high reactance transformer having a primary winding and at least one secondary winding; means for connecting said primary winding to said source through a condenser; means for connecting said secondary winding to said discharge device; and a semi-conducting resistor the resistance of which remains high when it is subjected to the voltage of said secondary winding under load and decreases largely and gradually when said resistor is subjected to the open circuit voltage of said secondary winding during at least every other half-cycle, said resistor being connected in parallel with said secondary winding through at least a portion of said primary winding.

4. A circuit as defined in claim 2, comprising an inductive reactance connected in parallel with the source of current.

5. A circuit for energizing at least one gaseous electric discharge device, comprising: an alternating current source; a high reactance transformer having a primary winding, at least one secondary winding and means for connecting one terminal of said secondary winding to a point on said primary winding; means for connecting said primary winding to said source through a condenser; means for connecting the other terminal of said secondary winding to one main electrode of the discharge device; means for connecting another main electrode of said discharge device to a terminal of the primary winding different from that point of said winding which is connected to said one terminal of the secondary winding; and a semi-conducting resistor the terminals of which are respectively connected to said other terminal of the secondary winding and to said terminal of the primary winding and the resistance or" which remains high when it is subjected to the voltage appearing between said other terminal of the secondary winding and said terminal of the primary winding when the nominal discharge current of the discharge device occurs between said main electrodes and decreases largely and gradually when it is subjected to the voltage appearing between the same terminals when substantially no discharge current flows between said main electrodes during at least every other half-cycle.

6. A circuit for energizing at least one gaseous electric discharge device, comprising: an alternating current source; a high reactance transformer having a primary winding, at least one secondary winding and means for connecting one terminal of said secondary winding to a point on said primary winding; means for connecting said primary winding to said source through a con denser; means for connecting the other terminal of said secondary winding to one main electrode of the discharge device; means for connecting another main electrode of said discharge device to a terminal of the primary winding difierent from that point of said winding which is connected to said one terminal of the secondary winding; and a semi-conducting resistor the terminals of which are respectively connected to the terminals of the secondary winding and the resistance of which remains high when it is subjected to the voltage appearing between said secondary winding terminals when the nominal discharge current of the discharge device occurs between said main electrodes, and decreases largely and gradually when it is subjected to the voltage appearing between the same terminals when substantially no discharge current flows between said main electrodes during at least every other half-cycle.

References Cited in the file of this patent FOREIGN PATENTS 709,100 Germany July 3, 1941 

